The present invention relates to a clamping mechanism for securing an end of a rope to a winch drum.
Winches typically have a power driven, rotatable winch drum to which one end of a rope, usually fabricated out of wire, is secured. The other or free end of the wire rope is secured to the load that is to be moved or lifted. Such winches are frequently used to move extremely heavy loads which may exceed 70 tons and it is very difficult to securely attach the rope end to the winch drum in a manner that will prevent its slipping free when subjected to high tension forces caused by such heavy loads.
The winch drum is normally provided with an open ended compartment having spaced apart sidewalls and open front and rear ends. One end of the wire rope is inserted through the open front end of the compartment to lie in contact along one of the walls. A wedge member is then placed between the rope and the other wall of the compartment. The next step is to initially "set" the wedge to clamp the wire rope between the wedge and drum sidewall with enough lateral force to increase the friction between the wedge and the rope to a magnitude such that tension on the wire rope will tend to pull the wedge further into the compartment and create a wedging action against the wire rope end that will prevent its slipping free under full load. If the wedge is not properly set the rope end will slip free, allowing the load to fall or otherwise move freely with potential damage. The wedge is "set" by placing a driver, such as a punch, into the rear end of the compartment against the wide end of the wedge and then driving it further into the compartment with a series of powerful hammer blows to the punch. This clamps the wire rope end between the wedge and drum wall.
In theory, setting the wedge is a simple act. In actual practice setting the wedge can be difficult and time consuming. Four independent components, (rope end, wedge, driver and hammer) have to be simultaneously handled. The rope end and wedge must be inserted into the compartment, accurately aligned axially of each other in the compartment and then held in such alignment while the driver is placed against the wide end of the wedge. With these three components held in loose alignment with one hand the installer must then swing the hammer with accurate and powerful blows to drive the wedge into its initial set position.
The initial setting of the wedge is made more difficult when the winch is located in a small restricted compartment. For example, in a tank retrieval vehicle (used to "tow" military tanks), the winch is in a restricted compartment which is enclosed, thus placing the winch in almost total darkness even during daylight conditions. Not only is it difficult to see the wedge, the space available for the winch is such that it is also difficult to find room to swing the hammer. Under battle conditions time is of the essence, and with known designs reattaching the end of a broken rope can take too long, with undue risk that the rope attachment will fail under full load.
If the wire rope breaks, removal of the wedge to release the wire rope end is also difficult. A punch must be inserted through the open front end of the compartment and hit with a hammer to unseat the wedge.